The automotive industry is currently researching and developing automated vehicles including road safety and driverless vehicles applications and with this comes a motivation to connect more vehicles with each other and with the Internet. There is a perceived need for a vehicle-to-vehicle (V2V) communication system capable of establishing communication links between vehicles allowing very rapid and very reliable communication, beyond what 4G wireless network technologies can currently provide.
The third generation partnership project (3GPP) LTE and LTE-A wireless telecommunication technologies, which typically involve transmission rights being granted by a scheduler in an evolved NodeB (eNodeB), have certain limitations meaning that they are not entirely suitable for V2V communication. For example, latency rises with the number of users in a cell and every data packet, such as a data packet between two nearby vehicles, is typically directed through the eNodeB, which introduces an uplink (UL) and a downlink (DL) communication can introduce delay, particularly in an overloaded cell. A single radio transmission along a direct path between source and transmission nodes is likely to be more efficient. D2D communication enables User Equipments (UEs) to discover and communicate with each other directly and allows communication delay to be reduced whist still allowing the infrastructure to retaining control of control plane functions such as radio resource allocation. A ProSe feature specified by 3GPP Technical Specification (TS) 23.303, July 2015 allows for ProSe Direct Discovery and ProSe Direct Communication, which enable UEs to discover and communicate with each other directly. In this specification D2D and ProSe can be used interchangeably. A direct radio link between two or more UEs is known as a “sidelink” (see 3GPP Technical specification (TS) 36.211), to distinguish it from conventional uplink and downlink connections between UE and eNodeB. Sidelink (SL) communications use a subset of the LTE UL time-frequency resources and use Single Carrier-Frequency Division Multiple Access (SC-FDMA), i.e., the similar transmission schemes as LTE uplink transmissions. The relevant SL channels are: PSCCH for SL control information; PSSCH for SL data; PSDCH for discovery announcements and PSBCH for broadcast of system information. Further in this description the PSXCH term is used to denote any of the SL physical channel. Any references in this specification to LTE can be interpreted to include LTE and/or LTE-A.
There is a motivation to enhance the ProSe interface to meet the desirable features of V2V services over licensed and unlicensed spectrum, particularly to cope with vehicle speeds and carrier frequencies (e.g. up to 280 km/h; and up to 6 GHz) where transmission may potentially be less reliable due Doppler effects. There is also a motivation to enhance LTE UL for the same reasons. There are two general propagation effects that arise from motion of one or more of a transmitting and receiving UE. Firstly, there is a Doppler frequency shift for line-of-sight paths for transmitter and receiver. Secondly, there is Doppler spread for non-line-of-sight paths.
LTE/LTE-A may be one of the main candidate technologies to realize the “connected cars” concept and provide the vehicles with wireless connection among each other and to the Internet. To address the strong interest of the vehicle manufacturers and cellular network operators in the ‘connected cars’ concept, the LTE Release 13 study on LTE-based V2X Services has been recently discussed, for example as found in: RP-151109, “New SI proposal: Feasibility Study on LTE-based V2X Services”, LG Electronics, CATT, Vodafone, Huawei, 3GPP RAN Meeting #68, June 2015. The study objective may be to evaluate new functionalities and potential enhancements to operate LTE-based V2X services, for example vehicle-to-vehicle (V2V), vehicle-to-infrastructure/network (V2I/N), and vehicle-to-pedestrian (V2P).
The V2V services may be deployed in the 6 GHz band, although other bands are not precluded. Furthermore, in accordance to the legacy criteria the V2V operation may be supported for the high speed scenarios, for example up to 280 km/h relative vehicles speed. Therefore, in embodiments, LTE physical layer channels for V2V may be robust enough and may provide reliable performance in the high Doppler scenarios (i.e. up to 1.5 kHz Doppler frequency).
Enhanced PC5 transport channels (i.e. SL device-to-device (D2D) physical channels) may be considered to be used to enable direct V2V operation. At the same time, the “legacy” (i.e. previously known) LTE SL physical channels may be designed with the assumption of substantially lower maximum Doppler frequency. Therefore, it may be advantageous for certain enhancements to the SL physical layer design to be introduced to efficiently support V2V services. It will be appreciated by the skilled person that embodiments apply not only to LTE SL physical channels but also to LTE UL physical channels (non-SL) and demodulation of UL physical channels. In general, demodulation according to embodiments applies to LTE wireless communications originating from a UE, which includes SL communications and UL communications.